Most lighters sold in the world market today include a moveable burner tube for opening and closing the valve thus allowing the fuel to flow to be ignited and establish a flame. Initial thumb movement rotates a spark wheel to provide sparks for igniting the fuel at the burner tube tip. Immediately thereafter, the burner tube, which moves relative to the housing in a clearance provided therefore, is lifted by a lever arm which is operated by the force provided by the continuing thumb movement contacting a thumb portion of the lever at an end opposite the burner tube. This force on the lever acts through a pivot point to move the burner tube to an open position which allows fuel to flow from the supply to the burner tip. When the fuel arrives at the burner tube tip, it is ignited by the sparks to establish a flame. When the lighter is not used, a spring normally located under the thumb portion of the lever arm provides sufficient force to the lever arm to maintain the valve in a closed position. This force is capable of withstanding exposure to the usual handling and carrying conditions without opening the valve at times when at which it is not desired.
The force of the spring is generally on the order of about one pound. This force is sufficient to overcome fuel pressure which attempts to pen the valve (normally about 2-4 ounces) and for providing the incremental force required to seal the valve despite the possible existence of surface imperfections of the component parts in order to achieve a reliable seal enclosure of the burner (another 2-4 ounces), as well as to over come forces caused by minor obstructions between the movable burner tube and the housing which obstructions may cause increased friction during movement of the burner tube (estimated at approximately 4 ounces or less).
As the lighter is repeatedly ignited, the action of the spark wheel on the flint generates abrasive dust particles, which may enter the clearance between the movable burner tube and the housing. Also, lint or other fabric dust from the pocket(s) of the clothing in which the lighter is carried represent a further source of dirt which can enter this clearance. The lighter will also experience various climatic conditions, both hot and cold, both in low and high humidity, as well as contact with fluids or foods, and such conditions provide a source of additional contaminants which may impede the proper movement of the burner tube between the open and closed positions.
If these contaminants provide a force of an additional 4-6 ounces, then the force of the spring will be insufficient to properly close and seal the valve. It is not practical to substantially increase the force of the spring because this would impede the normal thumb operation of the lighter, making it more difficult and more cumbersome to establish a flame. Furthermore, if the spring pressure is, in fact, increased, the lever arm or other component parts can be damaged due to overstraining. Such higher forces can also cause irreversible deformation of certain component parts, particularly those of an elastomeric nature.
None of the prior art lighters of which the applicant is aware have recognized the totality of this problem. Accordingly, heretofor there have been no solutions for resolving such an unrecognized problem. The present application discloses a lighter which is rendered inoperative when contaminants accumulate between the burner tube and housing sufficient to impede the proper closing and sealing of the valve so as to prevent the escape of fuel when not intended. This result is obtained by providing a considerably smaller force for opening the valve in comparison to the force of the spring used to close the valve, in contrast to prior art lighters.